The objectives of the proposed research are to pilot test a new method for examining children's concepts of personal identity, to conduct a developmental study using this method, and to write up this research for publication. The method consists of testing children about the consequences to identity of hypothetical transplants of the brain and other body parts. This method offers distinct advantages over previous interview methods, providing a concise test of children's understanding of identity as a mental phenomenon, hence being centered in the brain. Preliminary investigations of present author have demonstrated the basic utility of the method. Variations in the method allow further testing of key hypotheses about children's developing understanding of identity in relation to their conceptions of individuality, self and others, and body part functions. These variations will be piloted and then formally tested in a developmental study.